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Thursday, 21 July 2011

A well-established finding in psychology is that successfully retrieving information from memory serves to consolidate the storage of that information. Each time your brain's filing clerk tracks down the right information, the more likely he is to find it another time. Psychologists call this the testing effect - practising retrieval of information is far more effective than simply re-studying that same material.

Can this benefit of testing be enhanced? Yes it can. A new study has provided the first ever demonstration of how to enhance the memory consolidation that occurs after correctly answering a test question. Bridgid Finn and Henry Roediger's important and somewhat surprising new finding is that following a correct answer with an aversive stimulus serves to enhance the consolidation of that memory. It's like punishing the filing clerk after each correct retrieval makes him even more accurate in the future.

Forty undergrads studied multiple lists of ten word-pairs, each featuring a Swahili word and its English translation. After each list of ten, they were tested. Presented with the Swahili, they had to answer with the English. Here's the important bit. If they answered correctly, one of three things happened immediately: a blank screen appeared, a neutral picture appeared (e.g. a fork) or a negative, aversive picture appeared (e.g. a dead cat).

After this pattern of study period and test had been followed for ten lists of ten word-pairs, the participants were then given a jumbo test of all 100 Swahili words. Here's the key result: for those items answered correctly in the earlier mini-tests, it was those that were followed by a nasty picture that were most likely to be accurately recalled in the final jumbo test. Earlier correct answers that had been followed by a neutral pic or blank screen were not so well remembered (and performance was equivalent across the blank/neutral conditions).

"These data are the first to show that arousal following successful retrieval of information enhances later recall of that information," the researchers said.

A follow-up study was similar to the first but this time correct answers in the initial mini-tests were followed by neutral or aversive pictures that appeared two seconds later, as opposed to appearing immediately as they did in the first study. This was to see if there was a narrow window beyond which a negative stimulus wouldn't any longer enhance the consolidating effect of correct retrieval. The results were just the same as for the first study, so even two seconds later, a nasty picture is still able to enhance the memory consolidating effect of a correct retrieval. Future studies are needed to test just how long after a correct retrieval this process is still effective, and to see if positive images exert a similar benefit.

Finally, the researchers looked to see if the presentation of a negative pic has its memory enhancing effect after items are merely re-studied, as opposed to recalled. A similar protocol with Swahili-English word pairs was followed as before, but this time, instead of mini-tests after each set of ten word pairs, the participants were simply given the pairs to study again, with each pair proceeded either by a blank screen, neutral picture or nasty picture. This time, there was no benefit of the negative pics. In fact, there was a trend for pairs to be recalled less often if they'd been followed by a nasty pic in the earlier study phase.

Why should negative images boost the consolidating effects of answering a test item correctly? Finn and Roediger aren't sure but think it has to do with links between the amygdala, which is involved in fear learning, and the hippocampus - a brain area involved in long-term memory storage. This is a rather vague account and doesn't explain why aversive stimuli only enhance memory after correct retrieval, not further study. By way of further context, a 2006 study showed the presentation of aversive images after to-be-learned stimuli was beneficial during the initial study of that material.

Post-script

I couldn't help wondering what Milgram would have made of this study. Recall that participants in his classic obedience research thought they were taking part in an investigation of the effects of punishment on learning. In Milgram's mock set-up, the "learner" was subjected to an electric shock each time they answered incorrectly. Of course, Milgram wasn't really studying memory, but this new article suggests that he could have been onto something. Somewhat paradoxically, though, it seems it's correctly answered items that ought to be followed by an aversive stimulus, not incorrect answers.
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8 comments:

Maybe participants were able to remember the words better because the negative / aversive pictures were more emotive than the neutral pictures? Perhaps the authours could include a positive pictures condition as well as blank screen and neutral to rule this out...what do people think?

Any memory advancements have obvious applications for education and revision but I am (understandably I think) hesitant over this one especially as the post script offers a Milgram reference. Maybe if you get the right answer you get an electric shock? Seriously though it's worth a think on whether there is any way to get the negative arousal in way that is appropriate in a learning environment.

I agree with the first commenter. Is it negative picture really the stimuli or is it just the emotion associated with it. I would think that in addition to dead cats, they would present playing kittens to measure some kind of positive affect. This would be keen to some kind of emotion triggered by recognition or emotional reward. It would also be interesting to compare it to some kind of monetary reward (like in the casino slots)...

I haven't read the paper, but on the basis of the summary agree with colleagues that one could use a range of 'positive' 'neutral' and 'negative' pictures (and get each participant to rate them afterwards - since for people that hate cats the experimental stimulus may actually have been positive ...). Quite a fun idea, strange it got published with such an obvious flaw - do the authors comment on that?

Hi All, thanks for your comments - yes, the lack of a positive condition was a glaring omission. I did allude to the need to investigate this at the end of the sixth paragraph: "Future studies are needed to test just how long after a correct retrieval this process is still effective, and to see if positive images exert a similar benefit." The authors do not provide any detailed discussion of this in their conclusion, but they say they are examining the effect of positive images.

I believe the authors interpret the negative stimulus as "arousing" not as "punishment". This is a really important distinction, as it is not about the instrumental effects of the negative image, but the attentional and possibly stress states.It also (as discussed by the authors) fits into the McGaugh model describing the effects of arousing events in modulation of memory storage

I agree with the first 2 commenters and it seems that negative pictures give more impact than a blank screen or neutral screen. But in my opinion, (even if there are no concrete studies yet regarding positive pictures as I did not read any studies about this yet)positive pictures would help in memory enhancement as I observed it personally with my team in their reactions when discussing issues.